The invention pertains to a stabilized hammer brush holder arrangement. More particularly, the invention relates to a hammer brush holder arrangement with a tilt-preventing mechanism utilizing a securing pin and a securing notch.
Pivotal bearings for hammer brush holders are disclosed in German patent DE 28 14 009 C3 and European patent EP 0 791 988 A1. The production and assembly process described therein is kept technically simple by providing the plastic hammer brush holder with molded cupped bearing receptacles at the end of the hammer brush holder facing away from the brush. These cupped bearing receptacles are configured to be plugged onto corresponding knife-edge bearings of a motor stator part. The motor stator part is preferably, in particular, a bearing bow. During operation, the brush ends of the hammer brush holder are pressed against the blade surface of a commutator by a pressure springs hooked into notches of the motor stator. In one embodiment, a pivotal bearing provided with individual pivot bearings on each end of the pivot axis thereof are designed in such a way that the hammer can also be locked firmly into position and axially secured by bearing bow stops projecting from between the individual pivot bearings.
A hammer brush holder with a tilt-preventing mechanism comprising a knife-edge bearing, a bearing bow, a securing pin and an additional axial position fixation mechanism is disclosed in German patent DE 24 17 028 A1. In particular, the reference discloses a commutator motor with a pivoting arms to prevent the tilting of the hammer brush holder. The ends of the pivoting arms facing away from the brush lead into diverging furcated lateral edges. These lateral edges form receptacles for a knife-edge bearing provided on a bearing bow. One of these edges has a hook-shaped end, which extends into an opening in the bearing bow. The hook-shaped end of the extension is constructed as an elastic spring that is tensioned to press against one edge of the opening. The width of the hook-shaped end conforms to the width of the hole, thus preventing the pivoting arm from tilting laterally from its operating position.
In addition, a hammer brush holder is disclosed in European patent EP 0 043 460 A in which a front plate and an end plate are provided for the axial fixation of the hammer brush and for securing the hammer brush against radial displacement or jamming.
One object of the present invention is to employ essentially this same design, which is advantageous in terms of production and assembly, while providing simple means to prevent the tilting caused by potential, externally applied lateral forces, which may arise, in particular, during production and transportation of the component. Such lateral forces, acting perpendicularly to the pivot motion for which the brush holders are designed, may cause the brush holders to be levered out of their pivot positions or placed into a permanent tilting position, with only one end of the brush pressed against the blade surface of the commutator.
According to one formulation, the invention provides a hammer brush holder arrangement with a tilt-preventing mechanism, including: a motor stator part; a hammer brush holder having a brush and having a pivotal bearing on the motor stator part; a projecting securing pin that engages into an associated securing notch, cupped bearing receptacles pivotally mounted onto knife-edge bearings; and axial securing stops for each of the knife-edge bearings. The projecting securing pin is provided on either the hammer brush holder or the motor stator part, which, in an operational position of the brush holder and the motor stator part. The corresponding securing notch is provided on the other of the motor stator part and the hammer brush holder. Together, the securing pin and the corresponding securing notch limit the tilting of the hammer brush holder in response to any force that acts perpendicularly to the pivotal motion about the pivotal bearing for which the hammer brush holder is designed.
The cupped bearing receptacles are provided either on the hammer brush holder on an end of the hammer brush holder facing away from the brush, or on the motor stator part. These cupped bearing receptacles are preferably located axially on either side of the securing pin, and are pivotally mounted onto at least one corresponding knife-edged bearing, which is provided on either the motor stator part and the hammer brush holder-whichever the cupped bearing receptacles are not provided on. The securing stop for each corresponding knife-edged bearing is preferably form-fitting, position fixating, tongue-shaped, and axially secures the knife-edged bearing.
Thus, it is possible to provide a mechanism for preventing such tilting on the basis of the hammer brush holders described in the Background section above, and having, in addition, the advantageous construction and assembly features presented in the above-recited objects of the invention. This involves a combination of a securing pin on the hammer brush holder and/or on the motor stator part, cooperating with a corresponding securing notch on the motor stator part and/or on the hammer brush holder. In addition, there are knife-edge bearings provided on either side of the securing pin, with tongue-like projecting axial stops associated with the knife-edge bearings, for providing a form-fitting positioning of the cupped bearing receptacles.
The securing pins and securing notches are preferably designed to work together to avoid, when the hammer brush holder and the motor stator part receiving the hammer brush holder are mutually in their operational position, an undesirable over-dimensioning resulting from a very secure interconnection. On the other hand, with the preferred design, if the hammer brush holder begins to tilt at even a small angle, further tilting is prevented because the securing pin runs into the edge of the surrounding securing notches. Once the shear forces that caused the tilting motion (which arise, in particular, nearly exclusively during assembly and transportation of the device) have passed, the hammer brush holder and brushes return automatically into their normal operational positions, preferably due to the spring tension exerted by the brush tension spring.